In the related art, there is known a seat slide device for adjusting a seat position of a vehicle such as an automobile in a vehicle front-rear direction (for example, refer to Japanese Patent No. 3788637 (Reference 1)).
The seat slide device is provided with a first rail and a second rail which both extend in a longitudinal direction, and the rails are joined to be capable of relative movement in the longitudinal direction (specifically, a vehicle front-rear direction). One (a lower rail) of the first rail and the second rail is fixed to a floor of the vehicle, and the other (an upper rail) is fixed to a seat of the vehicle. The first rail includes a plurality of lock holes which are open in a portion facing the second rail and which are shaped to extend in a short direction (specifically, a vehicle top-bottom direction). The lock holes are disposed to line up at an equal interval in the longitudinal direction of the first rail. The second rail includes a lock lever which is joined such that one end may move reciprocally in the short direction. The end portion of the lock lever is integrally provided with engaging protrusions which are capable of entering and exiting any of the plurality of lock holes in accordance with the reciprocal movement.
In a state in which the engaging protrusions of the lock lever are exited from the lock holes, since the engaging protrusions do not engage with the lock holes, relative movement becomes possible between the first rail and the second rail, and it becomes possible to change the seat position. In a state in which the seat position is set to a desired position, when the lock lever is operated and the engaging protrusions of the lock lever enter the lock holes, the engaging protrusions of the lock lever are locked into the lock holes. Accordingly, the relative movement in the longitudinal direction between the first rail and the second rail is restricted, and the seat position is fixed at the desired position.
In the seat slide device, the relative movement in the longitudinal direction between the first rail and the second rail is restricted due to the engaging protrusions of the lock lever abutting against the inner surfaces of the lock holes. Therefore, in the inner surfaces of the lock holes, the inner surface shape of the portion against which the engaging protrusions abut is defined as a shape capable of supporting the engaging protrusions (specifically, the lock lever) at a desired orientation.
Ordinarily, one end portion of the lock hole in the short direction is a base portion which blocks the lock hole, and the inner surface shape of the base portion is a shape which facilitates the manufacture of the first rail, where a portion corresponding to the boundary between the base wall and the side wall of the lock hole being formed as a curved surface or the like, and the inner surface shape of the base portion is not a shape capable of appropriately supporting the lock lever.
In the seat slide device, although the engaging protrusions of the lock lever do not abut against the base portions of the lock holes at ordinary times, the engaging protrusions may abut against the base portions of the lock holes due to variation in the engaging protrusions and the lock holes with the passage of time, shock applied to the device in accordance with a vehicle collision, or the like. In this case, since it may no longer be possible to appropriately support the engaging protrusions of the lock lever with the inner surfaces of the lock holes, this can become a cause leading to destabilization of the fixing state of the seat position.